1. Field of the Invention
The invention relates to a controller for a lithium ion secondary battery, and a vehicle including the controller for a lithium ion secondary battery.
2. Description of Related Art
In the specification, the word “secondary battery” means repeatedly chargeable battery in general. A lithium ion secondary battery that is an object to be controlled by a controller includes not only a single cell but also a battery pack in which a plurality of battery components are connected. Lithium ion secondary batteries assembled in a battery pack are referred to as battery components as needed.
For example, Japanese Patent Application Publication No. 2011-189768 (JP 2011-189768 A) describes a method of preventing or reducing the degradation of a battery. In this method, a charge current is reduced when the state of charge is high, and a discharge current is reduced when the state of charge is low. For example, it is also suggested that the state of charge and state of degradation of a battery are calculated on the basis of information about voltage, current and temperature and then a limit value of the charge current or a limit value of the discharge current is changed in response to a comparison between estimated degradation estimated in advance by cycle test, or the like, and actual degradation.
Japanese Patent Application Publication No. 2013-106481 (JP 2013-106481 A) describes that a target SOC is set in response to the state of degradation calculated on the basis of an increase or decrease in resistance value and then charge and discharge control is executed.
Japanese Patent Application Publication No. 2009-123435 (JP 2009-123435 A) describes that the amount of degradation is calculated on the basis of a bias of the concentration of ions due to discharging and then a discharge power is restricted.